As a technique related to the present invention, a system is proposed which counts the number of persons present in a vehicle based on an input image obtained by capturing an image of the vehicle from outside of the vehicle by a camera. PLT 1 and PLT 2 describe techniques that count the number of persons present in a vehicle by detecting faces and heads of persons based on an input image obtained by capturing an image of the vehicle by a camera from a position in front of the vehicle.